I am trying to connect my MacBook Pro running OS 10.7.4 to a Toshiba monitor. Where can I get the necessary driver software?
You don't need a driver or any software for a monitor to work. Unless you have a touchscreen monitor, for instance.
As long as you have the right hardware connection, you're good to go.
If you don't know what connectors you're dealing with:
The MacBook Pros from 2008 till now all have Mini DisplayPort ports. In addition, the mid-2012 models also have an HDMI port: MacBook Pro on Wikipedia.
And for the monitor, I'd guess you probably have a VGA connector. But it could also be DVI, HDMI, or something else (post a picture?).
Anyway, you'll probably need an adapter to connect your monitor. I'd suggest http://www.monoprice.com/.